Two Distinct Oxidation Dispersion Mechanisms in Pd−CeO2 Mediated by Thermodynamic and Kinetic Behaviors of Highly Dispersed Pd Species

Using environmental scanning transmission electron microscopy and a global optimization algorithm, we unraveled the preoxidation dispersion and direct dispersion mechanisms in Pd-CeO_{2}(100) systems, mediated by the behaviors of highly dispersed Pd species. At lower temperatures, Pd nanoparticles first undergo oxidation, followed by the dispersion of PdO nanoparticles. In contrast, at higher temperatures, Pd nanoparticles directly convert into highly distributed cationic Pd species. These distinct dispersion mechanisms are driven by the thermodynamic and kinetic differences of environment-dependent Pd1-2O and Pd1-4O species, providing a fundamental basis for precisely controlling catalyst dispersion states.